分类: 地球科学 >> 空间物理学 提交时间: 2017-03-10
摘要: Electromagnetic waves used for deep space communications are mainly affected by the charged particles ejected by the sun. These effects may result in degradation of communication quality or communication interruption. This paper discusses the effects of solar scintillation on electro-magnetic waves, including the scintillation index which is a measure of the intensity scintillation, the coherence bandwidth and the coherence time of deep space communication channel. The deep space communication channel under solar scintillation is modeled by using Rician fading channel according to the scintillation index. The coherence bandwidth will determine whether the channel is flat fading or frequency selective fading and the coherence time will determine whether the channel is slow fading or fast fading. The approach of choosing signal band width is determined by the coherence bandwidth and the coherence time with the change of the solar elongation angle. The simulation results show the bit error rate of the signal bandwidth chosen by the proposed approach is lower than a random choice.
分类: 生物学 >> 生物物理学 提交时间: 2016-05-05
摘要: Formaldehyde exposure is toxic to the brains of mammals, but the mechanism remains unclear. We investigated the effects of inhaled formaldehyde on anxiety, depression, cognitive capacity and central levels of glucocorticoid receptor and tyrosine hydroxylase in mice. After exposure to 0, 1 or 2 ppm gaseous formaldehyde for one week, we measured anxiety-like behavior using open field and elevated plus-maze tests, depression-like behavior using a forced swimming test, learning and memory using novel object recognition tests, levels of glucocorticoid receptors in the hippocampus and tyrosine hydroxylase in the Arc, MPOA, ZI and VTA using immuhistochemistry. We found that inhalation of 1 ppm formaldehyde reduced levels of anxiety-like behavior. Inhalation of 2 ppm formaldehyde reduced body weight, but increased levels of depression-like behavior, impaired novel object recognition, and lowered the numbers of glucocorticoid receptor immonureactive neurons in the hippocampus and tyrosine hydroxylase immonureactive neurons in the ventral tegmental area and the zona incerta, medial preoptic area. Different concentrations of gaseous formaldehyde result in different effects on anxiety, depression-like behavior and cognition ability which may be associated with alterations in hippocampal glucocorticoid receptors and brain tyrosine hydroxylase levels. (C) 2015 Elsevier Ltd. All rights reserved.